PCIe lanes

z170 chipset offers x8/x8 or x8/x4/x4 configs. 

if you go with an Nvidia graphics card (because they limit 16-lane cpus) your limited to 2-way sli.  depending on the board (like MSI's Gaming M7) they exploit the various upgrade paths via the PCH with pcie switches to enable 3-way "crossfire" (AMD's multi card solution) support. 

it gets really complicated with z170 and its flexible PCH I/O.  there are so many combinations it comes down to selecting the right board for your needs.  you would have to do a lot of research with each mobo manufacturer.  i still don't think you can get 2 vid cards plus a pcie ssd with this platform, but i could be wrong.  you can get 2 M.2 SATA ssd with 2 vid cards in the mobo i referenced and a lot of other storage configurations that aren't pcie.  

edit: i just checked the aforementioned mobo and it does look like it supports x8/x8/x4 configs and M.2 pcie ssd.  i would still shoot a call to them to make sure you can run two graphics cards plus an M.2 pcie ssd at the same time. 


Edited by db188 - 17 Sep 2015 at 3:42pm

There are a few high-end Z170 motherboards (Gigabyte Z170 G1 Gaming, EVGA Z170 Classified, ASUS Z170-WS, possibly others) that have PLX PCI-e switches on them. The PLX switch they use usually allows x16/x0/x16/x0 or x8/x8/x8/x8. But you must realize that there is no extra bandwidth to the processor; the PLX chip only redirects bandwidth. The PLX chip also consumes several watts of power and incurs a latency (140 ns or more) in communications between the processor and graphics cards. The latency isn't as critical as bandwidth in compute (scientific) applications, but for graphics it matters more.

The majority of SLI-capable Z170 motherboards are x8/x8 with the PCI-e 3.0 x4 going to the chipset. The PCI-e NVMe drives are supported by the High Speed I/O (HSIO) lanes that have Intel Rapid Storage Technology (RST) supported, which there up to 3 on the Z170 chipset. However, there are a lot of tradeoffs with the I/O, as you can see here: http://www.anandtech.com/show/9485/intel-skylake-z170-motherboards-asrock-asus-gigabyte-msi-ecs-evga-supermicro.

I haven't come across any comparisons with the Z170 latency, although I haven't explicitly looked for any, either. I would be interested in finding out about it, though.

You can actually do more high-speed storage on Z170 than X99 (or Z97), but the motherboard has to be configured correctly. The manufacturers really need to start publishing the block diagrams for their PCI-e lane and HSIO allocation so we know what is possible.